During the melee, one older man was seen on his knees pleading with police not to shoot.

Before the scuffle, black-clad protesters had thrown projectiles at police, including bricks and petrol bombs.

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Police had said water cannons would only be used at a “large-scale public disturbance”

Police also fired rubber bullets and tear gas, and used two water cannon vehicles to clear barricades and disperse crowds.

Images on social media showed the vehicles being driven through the streets of Tsuen Wan, where a group of demonstrators had set up roadblocks and dug up bricks from the pavement.

The vehicles are equipped with surveillance cameras and multiple water cannon nozzles, and police had said they would only be used in the event of a “large-scale public disturbance”.

Earlier this month, human rights group Amnesty International warned that the cannons could cause serious injuries and lead to further tensions.

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The clashes over the weekend marked the end of an uneasy peace between police and protesters

Activists have criticised the police for being heavy-handed during the pro-democracy rallies, which saw several people hospitalised after violent clashes on Saturday.

The latest round of violence followed a stretch of uneasy peace in Hong Kong. But on Saturday, a senior Hong Kong official warned that the mainland’s military could intervene during any civil unrest.

Maria Tam Wai-chu, deputy director of the Hong Kong SAR Basic Law Committee, told a seminar in southern China: “The soldiers stationed in Hong Kong are not straw men meant to just stay in the garrison, they are an important part of the ‘one country, two systems'”.

On Sunday another more peaceful rally was held comprising a few hundred people, some of them family members of the police, who called for a political solution to the crisis.

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Several police officers were taken to hospital after the clashes

A new level of determination

Saira Asher, BBC News, Hong Kong

For the second day this weekend an industrial neighbourhood in Hong Kong became a battleground. Parts of Tsuen Wan are known for triad gangs so tensions were high to begin with.

But as a thick fog of tear gas engulfed a major street, it became clear that the brief peaceful lull Hong Kong had enjoyed last week was well and truly gone.

The hardline group of protesters came ready-armed with bricks, petrol bombs and metal rods. And the moderate protesters egged them on from the sidelines, shouting “corrupt police” and calling them “piles of rubbish”.

Ordinary residents and spectators were red-eyed from the tear gas and hunching low as they crossed the overhead bridges. This weekend has been a return to the familiar scenes between the police and protesters, but with what seems like a new level of determination from the protesters.

Why are there protests in Hong Kong?

They were sparked by a now-suspended extradition bill that would have allowed Hong Kong to send criminal suspects to China for trial, but they have grown into a broader movement calling for democratic reform in the territory and an investigation into alleged police brutality against protesters.

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Media captionHow Hong Kong got trapped in a cycle of violence

On 18 August, about 1.7 million people attended a pro-democracy rally in central Hong Kong, according to organisers. Police put the figure much lower, at 128,000, counting only those at an officially sanctioned rally in the city’s Victoria Park.

There have been previous protests at Hong Kong International Airport as well as tourist spots in the city.

Hong Kong protests: A timeline of escalating tensions

3 April: Hong Kong’s government introduces legislation which would mean residents suspected of a crime could be extradited to China to face trial for the first time

9 June: An estimated one million people march to the government headquarters to show their opposition to the bill

12 June: Police fire tear gas and rubber bullets at the demonstrators for the first time

16 June: An estimated two million people take to the streets demanding Hong Kong leader Carrie Lam completely withdraw the bill. She had promised to indefinitely delay it the day before

21 July: Mobs of men wearing white shirts attack commuters in an underground station, the same day protesters defaced China’s Liaison Office in Hong Kong